Circular197—Platycrinites and associated crinoids from Pennsylvanian rocks of the Sacramento Mountains, New Mexico

By A. L. Bowsher and H. L. Strimple, 1986, 37 pp., 1 table, 70 figs.

Platycrinites and other genera of the crinoid family Platycrinitidae are abundant in the early Carboniferous and known from the Permian of East Indies as well, but their late Carboniferous record has so far been sparse and questionable. Doubt that platycrinitids existed during late Carboniferous was allayed when in 1969 Strimple and Watkins for the first time reported a platycrinitid calyx from the Pennsylvanian of Texas. The two genera and species of platycrinitids, Platycrinites nactus n.sp. and Exsulacrinus alleni n.gen. st sp., found in the collections described in this report, further confirm the existence of platycrinitids in the late Carboniferous. Similar types occur in the early Carboniferous in the Permian. The new genera and species described from the Sacramento Mountains confirm the existence of platycrinitids in the late Carboniferous.

The collection from the Sacramento Mountains also includes numerous other typically late Carboniferous crinoids: Lecythiocrinus sacculus n.sp., Laudonocrinus subsinuatus, Algaocrinus aff. marquisi, Parulocrinus aff. harrisae, Stenopecrinus glaber n.sp., and an indeterminate synerocrinid. Their discovery is thought to be due to the presence of outcrops of reef-type strata, i.e., rocks that are not usually exposed.

Crinoid workers have long recognized the enigma of absence of platycrinitid calyces in late Carboniferous strata, although they are common in the early Carboniferous and are known from the Permian strata of Timor, East Indies. It is exciting to find platycrinitid calyces in the Pennsylvanian rocks of the Sacramento Mountains. The occurrence of the platycrinitids in Grapevine Canyon, Sacramento Mountains, is believed to be a function of the reef-type strata of the Gobbler Formation present at the locality, a rock type of the Pennsylvanian not commonly exposed on the surface for examination. The incompleteness of the local geologic record is obvious.